Field of the Invention
The invention relates to an apparatus for occupant protection in a motor vehicle.
Published non-prosecuted German Patent Application DE 37 29 019 A1 discloses an apparatus for occupant protection in a motor vehicle with sound or structure-borne sound sensors. From the sound or structure-borne sound that is picked up, an evaluator distinguishes a collision from other noises and interference.
All the known apparatuses for occupant protection that have structure-borne sound sensors pick up longitudinal structure-borne sound deflections of a body component of the motor vehicle. If the body component is embodied for instance as an elongated metal bearer oriented parallel to the longitudinal axis of the vehicle, then this longitudinal bearer, in a front-end collision, is set into longitudinal oscillation either directly by the obstacle striking the longitudinal bearer, or indirectly via other body components. A structure-borne sound sensor, for instance in the form of a strain gauge mounted on the longitudinal bearer, picks up longitudinal oscillations of the longitudinal bearer. Because of their low amplitudes, these longitudinal oscillations must be amplified and evaluated at great effort and expense, if enough information is to be obtained from the structure-borne sound that is picked up, and moreover they occur only in the direction of impact.
It is accordingly an object of the invention to provide an apparatus for occupant protection in an motor vehicle, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices that can be produced at little effort or expense yet still furnishes an adequately sensitive signal for detecting a collision.
With the foregoing and other objects in view there is provided according to the invention, a sensor for picking up structure-borne sound secured to a body component, the sensor is set into structure-borne sound oscillation in the event of a collision, or is at least vibrationally coupled to the body component, in such a way that it picks up transverse components of the structure-borne sound oscillations, and thus a transverse structure-borne sound deflection of the body component. Depending on the structure-borne sound that is thus picked upxe2x80x94hereinafter called merely structure-borne soundxe2x80x94an evaluator controls an associated occupant protection device of the motor vehicle.
The advantage of the apparatus of the invention is in particular that the sensor that picks up transverse structure-borne sound deflections furnishes an electrical signal that represents useful oscillations sufficiently sensitively and is sufficiently insensitive to interference factors such that a collision with the vehicle can be detected with no uncertainty by the measured structure-borne sound. A transverse structure-borne sound is picked up regardless of the direction from which the collision occurs.
The following discussion will simply refer to the evaluation of the structure-borne sound in conjunction with the evaluation of the electrical signal furnished by the structure-borne sound sensor.
In accordance with one feature of the invention, the structure-borne sound sensor are disposed in a control unit for occupant protection in a motor vehicle. Such a control unit is conventionally solidly connected to a body component, for instance being screwed to it. The existing disposition of such a control unit can advantageously be used, by a suitable disposition of the structure-borne sound sensor in the control unit, for picking up transverse structure-borne sound deflections, without requiring that the structure-borne sound sensor be disposed remotely from the control unit and electrically connected to the control unit and the evaluator in it over lines that are vulnerable to interference and are hard to install. The control unit is preferably disposed approximately centrally in the vehicle in the tunnel; the vehicle tunnel itself is embodied as a rigid body component, or is connected to such a body component, such as a longitudinal bearer.
Another feature of the invention is the advantageous embodiment of the structure-borne sound-sensor. Tripping of the occupant protection device is initiated preferably in dependence of the evaluation of these parameters; besides evaluating the structure-borne sound, it is advantageously possible for still other sensed variables, such as occupant or occupant position detection, to enter into a final tripping decision.
Another feature of the invention is the advantageous refinement of the apparatus, in which the occupant protection device is tripped in dependence of both the structure-borne sound that is picked up and an acceleration that is picked up by an acceleration sensor. Such an apparatus has the advantage that to trip an associated occupant protection device, a collision must have been detected by two sensors based on different physical principles. This prevents tripping caused by a defective sensor, interference signals, or vibration signals caused for instance by traveling over a gravel surface, and it substantially increases the tripping safety and reliability of the overall apparatus.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in an apparatus for occupant protection in a motor vehicle, it is nevertheless not intended to be limited to the details desired, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.